It has been common practice for sometime in the truck rental industry to supply with the truck a ramp to facilitate loading and unloading the truck. A significant advance was made in this art when inventors recognized the possibility of providing a storage space for the ramp beneath the truck floor between the longitudinal frame members of the truck chassis.
Storage of the ramp in the frame of the truck offers several advantages. Such storage is outside the cargo space so it does not take up that valuable space nor interfere with articles stored in the cargo space. Furthermore, this storage arrangement positions the ramp at the rear of the truck immediately beneath the floor of the truck body where it is accessible to the user who merely needs to withdraw the ramp from its storage space and place it in use.
Representative prior art arrangements for frame storage of ramps are disclosed in a series of three United States patents granted to John C. Abromavage and Henry S. Shattles, namely: U.S. Pat. No. 3,511,393 granted May 12, 1970 for "RAMP ASSEMBLY"; U.S. Pat. No. 3,559,826 granted Feb. 2, 1971 for "AUTOMOTIVE CHASSIS"; and U.S. Pat. No. 3,713,662 granted Jan. 30, 1973 for "CHASSIS WITH STORAGE SPACE".
All of the aforementioned Abromavage et al patents disclose releasable latches for locking the ramp in its stored position to prevent accidental dislodgement of the ramp when the truck is moved. There are no provisions, however, for locking the latches themselves. Consequently, with the arrangements of the '826 and '662 patents the ramps are exposed to theft when the truck is left unattended. In the '393 patent a rather elaborate and costly set of pivoted arms prevent the ramp from becoming completely detached from the truck.
Theft of loading ramps has become a major problem for operators of truck rental fleets. For ease of handling such ramps are usually made of aluminum which has considerable scrap metal value and encourages theft.
In an application for a United States Patent filed by William J. Curry on Apr. 10, 1989, Ser. No. 07/335,749 now U.S. Pat. No. 4,941,703 for an invention entitled "TRUCK RAMP STORAGE SYSTEM" and assigned to the same assignee as the present application, there is disclosed a system for interconnecting a latch on the truck body access door with a ramp movement blocking member. With this system, when the door is latched the ramp, if properly stored, is blocked against removal from its storage space beneath the floor of the truck. When the user locks the door latch he automatically locks the ramp in storage.
A disadvantage of the Curry system is the inability to transfer the system from one truck to another. In some instances the greatest risk of ramp theft occurs when the vehicle is in a storage yard at the rental facility. The risk is considerably less when the vehicle has been rented and is being attended to by the renter. There is a need, therefore, for a ramp anti-theft system which can be easily applied to trucks in storage, but can be removed when the trucks are rented and applied to other returned vehicles.